Automatic door systems are commonly used in a wide variety of different applications. For instance, automatic doors may be used to provide facilitated entry to and exit from structures such as buildings, vehicles, garages, elevators, and the like. Automatic door systems may generally include one or more doors, at least one sensor for detecting a person or object approaching and/or passing through the doors, at least one drive mechanism for opening or closing the doors, and a control unit for managing the overall operation of the door system. Automatic door systems may be configured to any one of a variety of different configurations. For example, the one or more doors of an automatic door system may be foldably, slidably, rotatably or hingably disposed along a common pathway thereof.
As with most automated systems, automatic door systems are left to operate continuously for extended periods of time, and generally, without supervision. Accordingly, it is increasingly important to provide automatic door systems with sufficiently reliable safety measures to ensure the safety of users and passengers. Although currently existing door systems are provided with several measures to safeguard passengers, there are several drawbacks. In elevator door systems, for example, it is common to use one or more automatic sliding doors. Detection devices may be provided to detect the presence of passengers or other obstructions in the path of the doors before and during closure to prevent harm to passengers, and further, to prevent damage to the door system. In the event of an obstruction, typical elevator door systems may be configured to prevent the elevator doors from closing further and reopen them.
One currently known system for detecting objects in the path of an elevator door places a light beam in a path across the door opening and uses a sensor to detect an interruption of the light beam, which would occur if an obstruction is in a pathway of the door. Upon sensing the interruption, the sensor issues a signal to alter the control of the door operation and reopens the door. However, such a system only detects obstructions in the path of the door and does not detect other issues that may prevent the door from closing properly such as a malfunctioning door track or motor.
Another known system for detecting door obstructions includes an incremental encoder for providing speed or position feedback. The encoder operates by having a rotatable encoder shaft connected to a door motor shaft so as to rotate conjointly therewith. The number, direction and speed of encoder shaft rotations thus indicate the direction of movement, speed and position of the elevator door. Thus, the encoder provides the capability to detect deviations in the motion of the door.
Another known system for detecting door obstructions includes a current sensor to detect an increase in a load of a door motor. This detection system determines that an obstruction exists if a current of the door motor increases. However, variations in a mechanical load, such as the weight of the landing doors in the elevator system, influence the performance of this type of detection system. The weight of the landing doors can vary significantly from landing to landing. The motor current is adjusted to provide compensation for the varying weight such that a desired speed profile is achieved. For example, a relatively heavy door requires an increased motor current. The increased current, however, can be falsely interpreted by the detection system as an obstruction. Additionally, costs associated with the sensor and its associated components, such as means to transmit information from a high voltage point to a low voltage point, are relatively high.
In light of the foregoing, the present application aims to resolve one or more of the aforementioned issues that can affect conventional door systems.